You want at least 2" but don't go over 2.5 inches or you'll hurt yerself. 2.25 is probably best. The exhaust won't do much unless you get a good set of headers. I would highly recommend Downey off-road. Yes, that seems like a good deal to me on the flowmaster and tubing. Just make sure they don't use a bunch of slip fits and filler crap
![Beer Chug\'n :beerchug:](https://board.marlincrawler.com/Smileys/marlin/beerchug.gif)